When Zim makes a huge scene over his inability to eat lunch food, he overhears one of the girls at school talking about how inhuman he seems to be and how he has no friends. In an attempt to appear more normal, Zim decides to spend time with a student named Keef, though Zim soon finishes his plan and he considers himself normal, so he tries to get Keef to leave him alone. Much to Zim’s chagrin, however, Keef continues to follow Zim around, so Zim decides to take unorthodox measures to ensure Keef leaves him alone.

After Zim watches an old movie where some invading aliens are defeated by some bacteria, he begins to study germs more. However, when he discovers that such germs truthfully are everywhere, he begins a crusade to kill every germ in his headquarters so that he can be safe, which is helped by the fact that Gir had some cleaning spray handy in the house; though when the cleaning bottle runes dry, Zim must attempt to go to the store and get some more, despite the fact that he knows just how many germs are out there.

Ms. Bitters is assigning students their mentors for Career Day through the use of an aptitude test and a machine. Both Dim and Zim attempt to get their desired professions on the test, in which Dib manages to get paired with a Paranormal Investigator while Zim gets stuck working at a fast food facility. However, when Zim misinterprets the 8 billion served sign and thinks that the individuals in charge of the company are the leaders of the planet, he becomes dedicated to his job in hopes of being promoted to Lord of All Humans. However, thanks to the alignment of the planets, Zim is about to go through some uncontrollable changes that could jeopardize his mission; which Dib is looking to exploit, though both Zim and Dib find their situations to go much different than they anticipated.

While at skool one day, Ms. Bitters tells the class that they need a new pet hamster due to the orders of the skool’s board of directors. When the hamster arrives, all the children love the hamster because of how adorable it is, in which Zim decides to exploit that fact since the hamster could help make the humans too weak to resist him. Zim plants an Irken device on the hamster that will permit it to grow larger and be controlled by Zim, but when the hamster grows rampant and breaks free, Zim must attempt to stop the huge hamster from destroying his headquarters, all the while worrying about the growing military presence that may have no choice but to attack the hamster, which would ruin all of his efforts.

Zim finally finishes one of his self proclaimed brilliant inventions, a space-time-object-transfer device, in which he plans to send a giant robot into the past in order to put an end to Dib once and for all. However, when the robot isn’t compatible with the temporal field, he throws a rubber pig into the vortex instead, which turns out to be compatible and it causes Dib to crash his tricycle in the past. Zim decides to send many more rubber pigs into Dib’s past, which ultimately affect him in the future; though when Zim overdoes himself, he discovers that history isn’t something that should be messed with.

When Zim comes home from a lousy day at skool because he found out that Dib knows a flaw in his security system, Gir attempts to cheer him up by rubbing bacon oil all over his face. However, when Zim develops a pimple due to the grease, he fears that he will be considered abnormal and that it will jeopardize his mission. Zim believe he can use some acne medicine to get rid of the pimple, but when it only gets worse and when Gir draws a little face on the pimple, Zim believes all hope is lost; though Zim soon discovers the pimple has hypnotic powers and he hopes to exploit this new power in order to get Dib to reveal his secret.

When Gaz sees an advertisement for the new handheld gaming console, the Game Slave 2, she decides that she really needs to go to the mall in order to get one. However, when her father insists that she takes Dib to the mall as well, he forces her to wait until Mysterious Mysteries goes off, which causes them to arrive at the mall late. Gaz, in rage, tricks Dib into running off into the underground parking lot while she attempts to get a Game Slave 2; though Gaz discovers an annoying kid managed to get the last copy so she seeks to steal his copy, all the while Dib must attempt to get out of the underground parking lot, which is filled with rat-like people who just annoy him.

Professor Membrane has just unveiled a world changing machine that will completely remove the entire need for fuel, though if the machine were to malfunction, it could cause a giant shockwave that would destroy all life on Earth. However, Professor Membrane refuses to turn the machine on until his children are present, in which Dib is absent because he is attempting to prevent Zim from sabotaging the machine. However, things soon take a turn for the worse as Dib falls into one of Zim’s traps and the crowd in front of Professor Membrane beings to grow uneasy over the fact that they’ve waited so long, so Professor Membrane decides to send Gaz to go find Dib and put an end to his foolishness.

The skool is holding a candy drive in order to get some finances, in which the individual who sells the most chocolate bars will get a secret mystery prize. Zim becomes interested and he attempts to find a way to sell the most chocolate bars, which causes Dib to get into the contest in order to gain a defeat over Zim. Zim soon realizes, however, that he may have to take drastic measures in order to sell more candy bars than Dib.

When Zim is attempting to explain to the Almighty Tallest that the humans are both dumb and tall, he gets interrupted when the doorbell rings and his transmission to the Tallest is cut short. The two individuals at the door claim to be human, but Zim doesn’t believe them and he attempts to tell them that their spaceship is jamming his signal; they respond by merely sacking both Gir and Zim and taking them to their spaceship. Will Zim be able to get back to his base and finish his report to the Tallest, and what will Zim do to the two aliens who dared to capture him?

The Almighty tallest are examining a storage planet in order to send valuable goods to the Invaders to help them on their missions. They decide to send a Megadoomer Combat Stealth Mech to Invader Tenn to help her conquest of the planet Meekrob and they decide to send a box of malfunctioning SIR units to Invader ZIM, but when the two packages addresses are switched by an angry slave, ZIM gets the Megadoomer and plans to use his new gift from the Tallest to put an end to Dib once and for all.

When at skool one day, a child comes into class late because his head was itchy, which Ms. Bitters recognizes that it was due to lice. Before she can do anything, however, the lice infect the rest of the students in the class, so Ms, Bitters informs the Delouser, who proclaims martial law and the children are taken into separate rooms. However, Zim shows no sign of being infected by the lice, which causes the Delouser to take special interest in him.

Zim's Yuletide plan to overtake Earth by posing as Santa starts to backfire when he takes on characteristics of the Jolly Old Elf. Dib, meanwhile, tries to save the population from impending doom.

Gaz develops an unhealthy fondness for the flavor of pork.

Zim's former boss is mad at him for leaving, so he kidnaps him and makes him work at his old job on the planet Foodcourtia.